With the score tied at 3 in the seventh inning, Baker allowed starting pitcher Joe Ross to bat for himself with two outs and no one on base.
"That was an easy decision. He can hit," said Baker, who explained he wanted to save his pinch-hitters for later in the game.
That plan worked, as pinch-hitters Bryce Harper (infield single) and Clint Robinson (walk) each reached base in the ninth before starting left fielder Jayson Werth came through with a two-run single with the bases loaded and two outs as the Nationals beat the Philadelphia Phillies 5-4 on Sunday.
"As a kid you always want that last at-bat," Baker said.
Ross, who hit a deep fly to left in the second inning, singled in the seventh but was left stranded as Sammy Solis came in to pitch in the eighth. Former Phillie Jonathan Papelbon (1-2) gave up a go-ahead homer to Maikel Franco in the ninth, but Danny Espinosa had a single and eventually scored the game-winning run in the last of the ninth as Werth delivered against closer Jeanmar Gomez (2-2)
"It was fun. It took a while to get out there," Espinosa said of the post-game pileup, which was led by Saturday starting pitcher Tanner Roark. "I was trying to get a good pitch to hit."
Werth came through with a hard single up the middle on a 2-2 pitch after he took a strike on the inside part of the plate that Phillies catcher Cameron Rupp couldn't hold.
"He has been a clutch man," Baker said of Werth. "Clutch men love to be in that situation."
The winning rally was aided when Harper reached on an infield single with one out in the ninth. The call stood after a challenge by Phillies manager Pete Mackanin as first baseman Tommy Joseph, a former catcher, tried to touch the bag with his foot twice.
"I believe if he didn't go back with his foot to touch it," Mackanin said. "If the side of his foot was touching the base he was definitely out, but he went back, it's like when a guy tags a guy but then goes back to tag him even though he didn't tag him the first time, it looks like he didn't. I believe, from what I saw on the replays, if he didn't go back with his foot, I believe they would've called him out."
"I wasn't sure. It was too close," Joseph said. "I couldn't feel it. Obviously if I couldn't feel it, that's why I went back and tried to tag him. I saw the replay on the board. I don't think I need to look at it. I think they got the call right."
The Nationals (39-24) are a season-high 15 games over .500 and have won six of their last seven. The Phillies (29-34), now a season-low five games under .500, have lost the last six to Washington.
The Phillies tied the game at 3-3 in the sixth as Odubel Herrera had an RBI double and Freddy Galvis singled to drive in Herrera.
Philadelphia's Cody Asche hit his first homer of the year in the fifth, a solo shot down the left field line to trim the margin to 3-1 against Ross.
The only hit Ross allowed in the first four innings was a clean single with two outs in the first to Franco, who had two hits.
Espinosa led off the second with his 11th homer of the season to give Washington a 3-0 lead against Adam Morgan, the Phillies starter. The switch-hitter, batting righty against Morgan, went deep for the eighth time in 15 contests.
Morgan, who entered with a 6.70 ERA, allowed three earned runs in 6 2/3 innings with a career-high eight strikeouts. David Hernandez came on to retire Michael A. Taylor for the last out of the seventh.
Ross, who lasted just four innings in his previous start, gave up three runs in seven innings with eight strikeouts and no walks before Solis took over in the eighth.
"Our pinch-hitters came through big time. That was huge," Baker said. "Espinosa had a huge at-bat."
NOTES: Mackanin was drafted by the Washington Senators in 1969 in the fourth round. After his playing career, Mackanin was a manager for the nearby Frederick (Md.) Keys in 1993 and the Bowie (Md.) Baysox the following year in the Baltimore Orioles' farm system. ... The red-hot Chicago Cubs come to Washington on Monday and RHP Kyle Hendricks (4-5, 2.90 ERA) will pitch against Nationals RHP Max Scherzer (7-4, 3.57) in the first game of the series. ... Philadelphia RHP Jerad Eickhoff (3-8, 3.68) will pitch at Toronto on Monday against Blue Jays RHP R.A. Dickey (4-6, 4.15). ... Washington got its first home series sweep since taking three games from the Minnesota Twins on April 22-24.